A coke oven is an apparatus for preparing coke by carbonizing coal (raw material) at high temperature. In the coke oven, coal is charged in a carbonization chamber, heated to 1100° C.˜1340° C. and then maintained at the same temperature for a predetermined time to carbonize the coal. Here, in order to maintain such a temperature state, air and fuel gas are supplied into a combustion chamber.
A coke oven is equipped with a plurality of independent carbonization chambers, and each of the carbonization chambers is provided with a gas rising pipe.
Such a coke oven generates coke-oven gas (COG), which is a volatile gas, during the process of carbonizing the coal stored in each carbonization chamber. This coke-oven gas is discharged through the gas rising pipe of the coke oven.
The coke-oven gas discharged through the gas rising pipe of the coke oven includes a large amount of environmental pollutants, such as dust, tar and the like, together with volatile materials. In order to remove such environmental pollutants, generally, they are collected in a gas collection pipe, and then sent into a post-treatment process.
Meanwhile, coke-oven gas is mostly reused as fuel in an iron mill by a refining process. With the increase in the usage of coke-oven gas, methods of increasing the usage of coke-oven gas have recently been researched and developed.
In relation to such research and development, various conventional technologies are disclosed.
Japanese Unexamined Patent Application Publication No. 2000-144142 (2000 May 26) discloses “a method of removing carbon attached to a carbonization chamber of a coke oven”.
This method is a technology of removing carbon attached to a carbonization chamber of a coke oven by injecting a gas mixture including carbon dioxide and steam into the carbonization chamber, and is characterized in that carbon dioxide (steam) and air is alternately provided in order to prevent the extreme rise and fall of temperature in the carbonization chamber at the time of gas injection.
Further, Korean Patent Registration No. 10-1082127 (2011 Nov. 3), filed and registered by the present inventor, discloses “a method of increasing the amount of coke-oven gas using carbon dioxide”. This method is a technology of increasing the amount of coke-oven gas by reacting high-temperature carbon with carbon dioxide and water using the waste heat generated from a coke oven, and is characterized in that carbon dioxide, water or a mixture thereof (gasifying agent) was supplied into a gas way in a carbonization chamber of a coke oven, and thus the gasifying agent reacts with carbon in the carbonization chamber, thereby increasing the amount of coke-oven gas.
The above-mentioned conventional technologies disclose methods of increasing the amount of coke-oven gas as well as recovering waste heat from coke-oven gas by injecting carbon dioxide and water into a coke oven to induce an endothermic reaction with high-temperature carbon.
However, the present inventor ascertained that various problems occurred when the amount of coke-oven gas was increased by the conventional technologies.
In order to confirm the above problems, the present inventor made experiments on the change in temperature of a gas way located at the upper portion of a carbonization chamber of a coke oven and the change in amount of generation of coke-oven gas over time, assuming that the operation time of the coke oven in one cycle is set to 24 hours. The results thereof are shown in FIG. 1.
As shown in FIG. 1, it can be ascertained that the temperature of the gas way located at the upper portion of the carbonization chamber was maintained at 500° C.˜1100° C. and that the amount of generation of coke-oven gas started to increase rapidly in about 6 hours, was maximized in about 10 hours, and decreased rapidly in about 13.5 hours. These numerical results may be changed by various factors, such as rate of temperature increase, structure of a coke oven, amount of charged raw material, etc., but the forms of generation of coke-oven gas are similar to each other.
According to this change in amount of generation of coke-oven gas, carbon dioxide must be introduced when the amount of generation of coke-oven gas is less than the average amount thereof. Therefore, when carbon dioxide is introduced therebefore, there is a problem in that it moves together with coke-oven gas in the gas way, so the effective residence time thereof in the gas way is insufficient, and thus the reaction time thereof with carbon in the gas way is also insufficient.
That is, a predetermined level of residence time can be secured only when carbon dioxide is introduced in 14 hours, and an endothermic reaction of carbon dioxide with carbon attached to a coke oven occurs even when the temperature of coal charged in the coke oven reaches 800° C. or higher. Therefore, there occurs a problem that a carbonization region, which can be used at the time of a reaction of carbon dioxide and carbon, is limited to a predetermined region.
Meanwhile, for the purpose of treating coke-oven gas, a coke-oven gas treatment system is disposed at the rear end of a coke oven. Here, when the amount of coke-oven gas is increased by the introduction of carbon dioxide, a part of unreacted carbon dioxide is introduced into a hydrogen sulfide (H2S) removal system to remove H2S, whereas most of unreacted carbon dioxide is supplied to a subsequent process to remove combustible components from coke-oven gas, thus lowering calorific value. Further, in this case, carbon dioxide, instead of H2S, is removed by the hydrogen sulfide (H2S) removal system itself, thus lowering H2S removal efficiency.
It is to be understood that the foregoing description is provided to merely aid the understanding of the present invention, and does not mean that the present invention falls under the purview of the related art which was already known to those skilled in the art.
Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method of increasing the amount of coke-oven gas, wherein the amount of generation of coke-oven gas can be increased by optimizing the starting point of introduction of steam, the reaction rate of steam with carbon being higher than the reaction rate of carbon dioxide with carbon, into a coke oven and thus maximizing the reaction time of steam with carbon in the coke oven.